Integral Looks at the Cosmos Through Gamma Glasses

Photo Credit: ESA, F Lebrun (CEA-Saclay)

The central regions of the Milky Way as seen by Integral in gamma rays. The brightest 91 objects in this image were classified by Integral as individual sources, while the others appear too faint to be properly characterized at this stage.

Scientists have opened a new window in the study of the formation of elements in the universe with a new space-based gamma ray telescope called INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory), launched by the European Space Agency in 2002. At the APS April meeting, researchers on the collaboration reported on the scientific highlights to date of the project.

Gamma ray photons are a million times more energetic than those of visible light, and can pass through matter with hardly any interaction. Even more powerful than X-rays, they are nonetheless blocked by Earth's atmosphere. Hence, gamma ray astronomy is largely space-based.

Positron annihilation is one source of gamma rays in the universe. Gamma rays are often created in the radioactive decays of short-lived elements inside such cosmic sources as supernovae and novae. Other sources include pulsars and micro-quasars.

Launched in October 2002, Integral uses two specially designed gamma ray telescopes to register these elusive rays. One provides the sharpest images of the gamma ray sky ever seen and the other measures the energies of the gamma rays with unprecedented accuracy. The telescopes work in tandem with an X-ray monitor and an optical camera. According to Roland Diehl of the Max Planck Society in Garching, Germany, this is the first time scientists have routinely been able to take several different measurements concurrently. This capability is expected to allow a clearer identification of the gamma ray sources.

Diehl reported that thus far the collaboration has observed one gamma ray burst per month during its first six months of operation.

The researchers have discovered ten new gamma ray transient sources, and have been able to produce the first map of parts of the galactic plane, based on the gamma rays emitted by decaying atomic nuclei.

It is hoped that Integral will also shed light on such mysteries as how black holes interact with their surroundings; supernova explosions and their role in forming chemical elements; and the specific nature of powerful gamma ray bursts.